1. Field of the Invention
The present invention relates to a recording medium suitably used in ink-jet recording. It also relates to a recording medium that can achieve a superior ink receptivity and recorded-image sharpness, and may cause beading and bleeding with difficulty.
The present invention further relates to a recording medium and a method for ink-jet recording using the same that can achieve a superior ink receptivity and recorded-image sharpness and may cause beading and bleeding with difficulty, even when ink is applied in a large quantity per unit area as in instances in which full color images are formed at a high density.
The beading mentioned in the present invention refers to a phenomenon in which dots irregularly move in the plane direction of the surface of an ink-receiving layer when ink is still fluid, before it is fixed in the ink-receiving layer, thus forming new aggregates together with adjacent dots to cause an unevenness in the density of recorded images.
The bleeding also refers to a phenomenon that edges of boundaries of multi-color printed areas can not be resolved because of feathering caused when ink is still fluid before it is fixed in the ink-receiving layer.
2. Related Background Art
Ink-jet recording has attracted notice as a recording method that makes less noise and can perform high-speed printing and multi-color printing. Hitherto having been used as recording media used in this ink-jet recording are papers commonly available, recording media called ink-jet recording papers, comprising a substrate provided with a porous ink-receiving layer, and light-transmissive recording media for OHP (over-head projectors).
In recent years, with improvement in the performance of ink-jet recording, such that the recording is performed at a higher speed and in more multi-colors, the recording media are simultaneous and increasingly required to have higher and more extensive properties.
In particular, it is necessary for the light-transmissive recording media to satisfy the fundamental requirements that;
1) they have excellent light-transmission properties; PA1 2) they have excellent ink absorptivity; PA1 3) dots are substantially round in shape, and have smooth peripheries; PA1 4) dots have a high OD (optical density) and are free from blurs on the dot peripheries; PA1 5) no beading is caused; etc.
In particular, the beading and bleeding are remarkably seen when a large quantity of ink is simultaneously shot on a recording medium as in instances in which a recording head having a plurality of ink ejection orifice (nozzles) is used, or instances in which full color images are formed using multi-color inks.
In ink-jet recording techniques, the beading that may lower the image quality level and slow the ink-fixing rate is coming to be a matter of a great account as recording is performed at a higher speed and in more colors using a multi-nozzle. The bleeding that may bring about a lowering of the resolution of images has also come to be a matter of a great account as nozzles are used in a higher multiplicity.
Various studies have been made so as to satisfy the above performances, and the result has been obtained to a certain extent. However, in the present circumstances, no recording medium has been known that has satisfied all of these required performances.
For example, a recording medium for ink-jet recording which comprises a substrate provided with a cover containing a water-absorptive resin is disclosed in Japanese Patent Laid-Open Gazette No. 57-173194. In this medium, a polymeric binder used in combination with the water-absorptive resin is used in an amount of from 0.05 to 5 parts by weight based on 1 part by weight of the water-absorptive resin, and coated with a weight of approximately from 1 g/m.sup.2 to 50 g/m.sup.2 in terms of solid content. However, this covering layer has, as a result, 5,000 or more of the number of the water-absorptive resin particles in a unit area of 1 mm.sup.2, resulting in a lowering of light-transmission properties and causing a high haze. This is not desirable for the transmitted-light viewing in slide projectors, OHP or the like.
Japanese Patent Laid-Open Gazette No. 61-24494 also discloses an OHP film comprising a transparent film coated thereon with fine particles having transparency. This, however, comprises the fine particles with a laminated structure, and hence has the disadvantage that it causes a high haze.
For further examples, Japanese Patent Laid-Open Gazette No. 60-46290 discloses an OHP film formed of a coating comprising a highly water-absorptive polymer and a water-insoluble binder, and Japanese Patent Laid-Open Gazette No. 63-151477 discloses an OHP film comprising a highly water-absorptive resin and a solvent-soluble resin which are used in combination.
Even such recording media, however, can not simultaneously satisfy the requirements of ink fixability and prevention of occurrence of a beading and bleeding when the ink has been applied in a high density and a large quantity.